Fig. 1: Active Janus colloids climb a wall.
A Experimental set-up: glass wall dipped into a sedimented monolayer of passive colloidal particles, at Pes = 0, under a gravity \({\vec{g}^{\ast}}\). B–D Iso-density maps of the colloids at Pes = 0 (passive case) and for two activities Pes = 9.4 and Pes = 13.6. The iso-density values ϕ are from top to bottom 0.08, 0.12, 0.16, 0.24, and 0.3. The pale green arrow highlights the maximum height of the isodensity curve ϕ = 0.08 at the adsorption layer. The pale red arrow indicates the small depression of the density close to the wall. E Snapshot of the numerical simulation of an assembly of ABPs under gravity near a wall with alignment \(\tilde{\Gamma }=26\) and adhesion strength \(\tilde{\epsilon }=3.25\), respectively, at an activity Pes = 13 (see Methods for details). Isolines at densities ϕ = 0.08, 0.12, 0.16, 0.24, 0.3 are shown (from top to bottom). F Density profiles ϕ(z) predicted by our ABP model far from the wall (solid line), and in the adsorption layer (dashed line). The dotted line indicates the density ϕ = 0.08 from which the adsorption layer height ΔH is defined.
